STRATIFIED SQUAMOUS EPITHELIA PRODUCE MUCIN-LIKE GLYCOPROTEINS

The stratified squamous epithelia of the ocular surface, larynx, and v agina are mucus-coated epithelia, apices of which are subject to abras ive pressure from epithelia - epithelia interactions from eyelid, voca l cords, or vaginal folds, respectively. Mucus coats on these epitheli a have generally been considered to be derived from the specialized mu cin-producing cells embedded either in the epithelia or in adjacent ti ssues. Here we report the isolation, partial characterization, and cel lular localization of a mucin-like glycoprotein produced by these stra tified epithelia. In all three epithelia, the mucin-like molecule is p resent on cytoplasmic vesicles in subapical cells. As cells differenti ate to their apical-most position adjacent to their mucus coat, the mu cin-like molecule moves to the cell membrane where it is particularly prominent on microplicae folds. Lectin affinity chromatography was use d to isolate the molecule from rat vaginal and corneal epithelium. Iso lated material was approximately 60% carbohydrate and 40% protein. The major monosaccharide was N-acetylgalactosamine with lesser amounts of N-acetylglucosamine, galactose, mannose, xylose and fucose. Amino aci d analysis demonstrated the predominant amino acids to be glycine, ser ine, threonine and proline. These data plus PAS and Alcian blue bindin g to the isolate indicate a mucin-like glycoprotein.